The present invention relates to a projection display, and it relates, in particular, to a projection display characterized by including a rotation adjuster for adjusting an offset in illuminance distribution on a light source side.
Within the projection display of three (3) plate type, the optical distance of an optical path (hereinafter, being called an “optical path length”) differs from, for each of light components, being separated in the color, to reach onto a liquid crystal panel corresponding thereto, and at least one of the optical path lengths of the color component lights is longer, comparing to that of the other color component lights. Then, adjustment or compensation in the optical path length is achieved with using a relay optic system on the optical path for the color component light(s) being long in the optical path length(s) thereof.
However, with such the relay optic system, since the light emitting from the light source propagates while reversing up/down (i.e., vertically) and left/right (i.e., horizontally), then there occurs a case that the color component light irradiating upon the liquid crystal panel passing through the relay optic system and the color component light irradiating upon the liquid crystal panel without passing through the relay optic system are opposite to each other, up/down (vertically) and left/right (horizontally), in particular, on the illuminance distributions thereof.
In this instance, if there is an offset or deviation in the illuminance distribution on the light source side, there is a possibility that color unevenness is generated on a display screen. The offset of illuminance distribution on the light source side is generated due to various factors. Thus, due to offset or deviation in positions and/or configurations of elements for converting polarized lights (i.e., polarized light converter elements), which are provided within a light source and/or an optical integrator, there are cases that the illuminance distribution be asymmetric up/down (vertically) and left/right (horizontally), on the emission light from that polarized light converter element(s).
For example, in case when the polarized light converter element has an opening configuration of being vertically long (herein, “vertically” means the direction in parallel with a short side of the liquid crystal panel having rectangular shape), then the left/right direction is at the highest on frequency of generating the uneven irradiation (herein, “left/right” means the direction in parallel with a long side of that rectangular-shaped liquid crystal panel, i.e., the horizontal direction).
Herein, although the optical path length of a light in a blue color zone (hereinafter, being “B-light”), the optical path length of a light in a red color zone (hereinafter, being “R-light”) and the optical path length of a light in a green color zone (hereinafter, being “G-light”) differ from one another, but in case where there no color unevenness is generated on the display screen since there is no offset or dispersion in the illuminance distribution on the light source side, then as is shown in FIG. 6(a), shapes of the illuminance distributions are nearly equal to one another among the R-light, G-light and B-light, respectively, on the liquid crystal panel, and there is no chance that on a portion of one color having a weak light irradiation is projected on a portion of other color having strong irradiation to build up a picture; i.e., there is no chance of generating the color unevenness on the display screen. The vertical axis in FIG. 6(a) shows a potion in the width direction on the liquid crystal panel, while the vertical axis the height or intensity of illuminance at the position in the width direction on the liquid crystal panel.
On the contrary to this, in case when the optical path length of the B-light differs from those of the R-light and the G-light, and thereby causing the offset or dispersion of the illuminance distribution on the light source side, then as shown in FIG. 6(b), the illuminance distributions of the R-light and the G-light irradiating upon the liquid crystal panel through a non-relay optic system differs from the illuminance distribution on the liquid crystal panel of the B-light. For this reason, strong illuminance portions of the R-light and the G-lights are projected on a weak illuminance portion of the B-light, and also a strong illuminance portion of the B-light is projected on weak illuminance portions of the R-light and the G-lights; thereby generating the color unevenness on the display screen.
Then, in Japanese Patent Laying-Open No. 2004-226814 (2004), for example, there is proposed a technology for bringing the configuration of illuminance distribution on the liquid crystal panel of the B-light to be equal to those of the illuminance distributions of the R-light and the G-light, while disposing a light shielding means at an end portion of a relay lens building up the relay optic system, so as to shield a portion of the B-light.